This invention relates to a preferably hermetic motor-compressor unit of the type comprising a usual drive shaft operated by a known electric motor and acting on a compressor section for a fluid, for example a refrigerant fluid, comprising a piston associated with a connecting rod operated by the aforesaid shaft, said piston moving within the bore of a corresponding cylinder in which it compresses said fluid.
In a motor-compressor unit of the aforesaid type the connecting rod has to be connected to the compressor section. This means that known machining work has to be carried out on the piston, resulting in considerable construction time and cost for this section, which are reflected in the overall manufacturing time and cost of the motor-compressor unit.
In addition, in hermetic motor-compressor units the pistons of the compressor sections are not provided with piston rings for reasons related to the section construction cost, noise and the power dissipated by friction, in that the cost, noise and power dissipation all increase.